1. Field of the Invention
The present invention relates generically to microcapsules containing a hydrophobic liquid core. It also relates to the selection of specific materials for the cores and the capsules and preparation and uses of the microcapsules.
2. Background Art
Microencapsulation of various hydrophobic liquids is well known. Microcapsules have been suggested for encapsulation of perfumes, medicines, adhesives, dyestuffs, inks, etc. It has specifically been suggested to microencapsulate fragrances for use in liquid or solid fabric softeners. See, e.g., U.S. Pat. No. 4,446,032, Munteanu et al., issued May 1, 1984, incorporated herein by reference. The individual perfume and/or flavor compounds which can be encapsulated are also well known, having been disclosed in, e.g., U.S. Pat. No. 3,971,852, Brenner et al., issued July 27, 1976; U.S. Pat. No. 4,515,705, Moeddel, issued May 7, 1985; U.S. Pat. No. 4,741,856, Taylor et al., issued May 3, 1988, etc., all of the above patents being incorporated herein by reference.
Microencapsulation techniques, including so-called "coacervation" techniques, are also well known, having been described, for example, in U.S. Pat. No. 2,800,458, Green, issued July 23, 1957; U.S. Pat. No. 3,159,585,Evans et al., issued Dec. 1, 1964; U.S. Pat. No. 3,533,958, Yurkowitz, issued Oct. 13, 1970; U.S. Pat. No. 3,697,437, Fogle et al., issued Oct. 10, 1972; U.S. Pat. No. 3,888,689, Maekawa et al., issued June 10, 1975; Brit. Pat. No. 1,483,542, published Aug. 24, 1977; U.S. Pat. No. 3,996,156 Matsukawa et al., issued Dec. 7, 1976; U.S. Pat. No. 3,965,033 Matsukawa et al., issued June 22, 1976; and U.S. Pat. No. 4,010,038, Iwasaki et al., issued Mar. 1, 1977, etc., all of said patents being incorporated herein by reference.
Other techniques and materials for forming microcapsules are disclosed in U.S. Pat. No. 4,016,098, Saeki et al., issued Apr. 5, 1977; U.S. Pat. No. 4,269,729, Maruyama et al., issued May 26, 1981; U.S. Pat. No. 4,303,548, Shimazaki et al., issued Dec. 1, 1981; U.S. Pat. No. 4,460,722, Igarashi et al., issued July 17, 1984; and U.S. Pat. No. 4,610,927, Igarashi et al., issued Sept. 9, 1986, all of said patents being incorporated herein by reference.
For certain utilities such as that disclosed in U.S. Pat. No. 4,446,032 it is desirable to have a strong capsule wall to permit preparation of finished compositions that contain microcapsules utilizing processes that tend to destroy capsule walls and yet have the capsules readily activated in some way during use.